Shadow Miku

Shadow Miku is a completely black Miku with red facial features.

Design
Except for her being coal black with red facial features, shoulder pads and elf shoes, she have long pigstails just like Miku.

She seems to be wearing a skirt like Miku.

Another difference is that Shadow Miku is cartoonish, not in anyway close to anime art style.

Personality
Her personality is chosen all to the fans.

Notable media
https://www.youtube.com/watch?v=oJvpxC0edNQ